Evelyne Migianu-Griffoni

Pharmacological and toxicological effects of Paronychia argentea in experimental calcium oxalate nephrolithiasis in rats

AIM OF THE STUDYnRenal protection and antiurolithiasic effects of two extracts of Paronychia argentea (PA), a traditional Algerian plant commonly known as Algerian tea, were evaluated. This study was carried out to determine whether the aqueous extract (APA) or the butanolic extract (BPA) of aerial parts could prevent or reduce calculi aggregation in experimental calcium oxalate (Ox) nephrolithiasis in Wistar rats.nnnMATERIALS AND METHODSnThe two extracts (APA and BPA) were administrated orally and daily, during 28 days to nephrolithiasic treated rats at the dose of 250, 500 mg/kg b.w. and 10, 20mg/kg b.w. respectively. Body weight, renal index, liver index, serum level of creatinine, uric acid, urea, K(+), Ca(2+), Mg(2+), Na(+) and transaminase (alanine aminotransferase, ALT; aspartate aminotransferase, AST), phosphatase alkaline activity (PAL) were evaluated following the 28 days treatment in rats. In addition histopathological changes in kidney and liver were stained in hematoxylin eosin (HE).nnnRESULTSnThe effect of the extracts could be advantageous in preventing urinary stone retention by reducing renal necrosis and thus inhibit crystal retention. In contradiction with APA, the two doses of BPA attenuated elevation in the serum creatinine (p<0.01) and blood urea levels (p<0.01) (nephroprotective effect). However, the increase in ALT (27%) and PAL (31-51%) serum levels and in the relative liver weights (p<0.01) in the groups treated with doses of APA may indicate that this extract has not a hepatoprotective effect against oxalate toxicity.nnnCONCLUSIONSnThe presented data indicate that administration of the butanolic extract of aerial parts to rats with NaOx induced lithiasis, and reduced and prevented the growth of urinary stones in experimental calcium oxalate nephrolithiasis in Wistar rats.

Adaptation of the base-paired double-helix molecular architecture to extreme pressure

The behaviour of the d(GGTATACC) oligonucleotide has been investigated by X-ray crystallography at 295u2009K in the range from ambient pressure to 2u2009GPa (∼20u2009000u2009atm). Four 3D-structures of the A-DNA form (at ambient pressure, 0.55, 1.09 and 1.39u2009GPa) were refined at 1.60 or 1.65u2009Å resolution. In addition to the diffraction pattern of the A-form, the broad meridional streaks previously explained by occluded B-DNA octamers within the channels of the crystalline A-form matrix were observed up to at least 2u2009GPa. This work highlights an important property of nucleic acids, their capability to withstand very high pressures, while keeping in such conditions a nearly invariant geometry of base pairs that store and carry genetic information. The double-helix base-paired architecture behaves as a molecular spring, which makes it especially adapted to very harsh conditions. These features may have contributed to the emergence of a RNA World at prebiotic stage.

In vitro assessment of liposomal neridronate on MDA-MB-231 human breast cancer cells.

Bisphosphonates have been used for decades in the standard therapy of bone-related diseases, including bone metastasis of various malignancies, and they might as well be toxic on early cancer cells themselves. In order to allow a better delivery of neridronate (a N-containing bisphosphonate with relatively poor activity), liposomes were evaluated in vitro on cancer cell lines (MDA-MB-231, U87-MG and Caco2). After chemical synthesis, this water-soluble molecule was encapsulated into liposomes containing DOPC:DOPG:Chol (72:27:1 molar ratio). The influence of neridronate (free or liposomal) on cell viability or proliferation after treatment was evaluated using the MTT method, as well as cell migration and invasion assays; these techniques showed a drastic improvement of the action of neridronate on MDA-MB-231 cells with an EC(50) 50 times lower when neridronate was encapsulated. Internalization of liposomes was followed by flow cytometry and fluorescence microscopy, demonstrating internalization via the endocytic pathway. Furthermore, since overexpression of matrix metalloproteinases (particularly MMP-2 and MMP-9) has been correlated to poor prognosis in many cancer types, detection of MMP expression is a satisfactory indication of the therapy efficiency and was then performed on treated cells. On MDA-MB-231 cells, MPPs expression was also significantly reduced by neridronate while entrapped in liposomes.

Bisphosphonate prodrugs: Synthesis and biological evaluation in HuH7 hepatocarcinoma cells

We investigated the biological effects of new synthesized bisphosphonates (BPs) on HuH7 hepatocarcinoma cells. BPs containing p-bromophenyl (R1xa0=xa0p-Br, Ph, 2) in their side chain were the more potent to inhibit HuH7 cell viability. In addition, phenyl diesterified analogues (R2xa0=xa0R3xa0=xa0Ph, 2a) were more potent than methyl (R2xa0=xa0R3xa0=xa0Me, 2b) or non-esterified BPs (2) inducing more necrosis suggesting that they better entered into cells. Phosphodiesterase inhibitor (IBMX) reversed the effect of the esterified BPs and not that of non-esterified ones suggesting role of cell phosphodiesterases to release active BPs. BP analogues inhibited HuH7 cell migration but esterified ones had no effect on invasion due to the hiding of phosphonic groups. All together, these results indicated the therapeutic interest of these new BP prodrugs.

Synthesis and biological evaluation of new bisphosphonate-dextran conjugates targeting breast primary tumor.

Bisphosphonates (BPs) have interesting antitumor effects as well in vitro as in vivo, despite their poor bioavailability in the organism after oral ingestion. To overcome this problem and reduce drug doses and secondary effects, we report the chemical synthesis of new bioconjugates. They were built with a nitrogen-containing BP as the drug covalently coupled to the carboxymethyldextran. This polysaccharide was used as a carrier, in order to increase BP lifetime in bloodstream and to target tumor cells which have a strong affinity with dextran. The efficiency of our vectorization system was biologically proved in vitro and in vivo on mammalian carcinoma models in mice.

Towards potential nanoparticle contrast agents: Synthesis of new functionalized PEG bisphosphonates

Summary The use of nanotechnologies for biomedical applications took a real development during these last years. To allow an effective targeting for biomedical imaging applications, the adsorption of plasmatic proteins on the surface of nanoparticles must be prevented to reduce the hepatic capture and increase the plasmatic time life. In biologic media, metal oxide nanoparticles are not stable and must be coated by biocompatible organic ligands. The use of phosphonate ligands to modify the nanoparticle surface drew a lot of attention in the last years for the design of highly functional hybrid materials. Here, we report a methodology to synthesize bisphosphonates having functionalized PEG side chains with different lengths. The key step is a procedure developed in our laboratory to introduce the bisphosphonate from acyl chloride and tris(trimethylsilyl)phosphite in one step.

Impact of alendronate and VEGF-antisense combined treatment on highly VEGF-expressing A431 cells.

Bisphosphonates, and more specially nitrogen-containing bisphosphonates, which are in current use for the treatment of bone diseases, demonstrate proapoptotic, antiproliferative, antiangiogenic and anti-invasive properties on tumor cells. The amino-bisphosphonate alendronate is considered as a potential anticancer drug. In the case of A431 cells, which express high levels of VEGF, it had a two-step effect. At 24h, the antitumor properties of alendronate were counterbalanced by a survival process, which consisted of an enhancement of VEGF expression (mRNA and protein secretion) and TGF alpha secretion. It was only at 48 h that alendronate displayed the expected antiproliferative and antiangiogenic properties. The first step, in which the PI3K pathway was engaged, could be prevented by the use of a VEGF-antisense oligonucleotide. The combination of such an antisense with small concentrations of alendronate (approximately 2 microM), which is of the order of clinically used concentrations, was shown to have an antiangiogenic effect as soon as 12h.

Bifunctional Tripeptide with a Phosphonic Acid as a Bronsted Acid for Michael Addition: Mechanistic Insights

Enamine catalysis is a widespread activation mode in the field of organocatalysis and is often encountered in bifunctional organocatalysts. We previously described H-Pro-Pro-pAla-OMe as a bifunctional catalyst for Michael addition between aldehydes and aromatic nitroalkenes. Considering that opposite selectivities were observed when compared to H-Pro-Pro-Glu-NH2 , an analogue described by Wennemers, the activation mode of H-Pro-Pro-pAla-OMe was investigated through kinetic, linear effect studies, NMR analyses, and structural modifications. It appeared that only one bifunctional catalyst was involved in the catalytic cycle, by activating aldehyde through an (E)-enamine and nitroalkene through an acidic interaction. A restrained tripeptide structure was optimal in terms of distance and rigidity for better selectivities and fast reaction rates. Transition-state modeling unveiled the particular selectivity of this phosphonopeptide.

Peptides holding a phosphonic acid: Easily recyclable organocatalysts for enantioselective C–C bond creation

GRAPHICAL ABSTRACT ABSTRACT A novel bifunctional organocatalysts library was developed as efficient tool for the stereoselective Michael addition of aldehydes with several aromatic nitroalkenes. Therefore, a phosphonic acid was used for the very first time as activating moiety in the field of organocatalysis. H-R-Pro-S-Pro-R-pAla-OMe (pAla stands for phosphonoalanine) was identified as the most effective one with up to 95:5 d.r. and 93:7 e.r over 12 GABA precursors examples. This catalyst was easily recycled and reused over 10 cycles without any significant loss of selectivity.

Methyl [hydr­oxy(phen­yl)phosphono­meth­yl]phospho­nate methanol solvate

The title compound, C8H12O7P2·CH4O, is a monoesterified bisphosphonate (or 1-hydroxymethylene-1,1-bisphosphonic acid). These synthetic compounds are widely used in medicine to inhibit bone resorption in diseases like osteoporosis, and are characterized by a stable P—C—P group and are thus analogs of inorganic pyrophosphate. By masking one or several ionizable groups, introduced as phosphonoester, it was anticipated the formation of prodrugs with higher lipophilicity that could facilitate the drug delivery and metabolization. Molecules are paired by intermolecular hydrogen bonds involving the phosphonic groups. In addition, dimers are connected side-by-side, building infinite ribbons along the a-axis direction; these ribbons are cross-linked perpendicularly along the b-axis direction via a methanol solvent molecule (disordered over two sites with occupancy factors ca 0.6 and 0.4), forming an extended intermolecular hydrogen-bonded network. The H atoms of the methyl group in the main molecule are disordered equally over two positions.